In the field of this invention it is known that it can be problematic to generate a video image of a scene with all moving objects removed. For example, in filming a motion picture the director may need to film an apocalyptic or relatively deserted view of the streets of a city. In order to do so, the director may “hire” streets of the city for a short period at a relatively affordable time (e.g., a Sunday morning). The streets would be blocked off and emptied and the filming would then take place. Clearly, such an approach is nevertheless extremely costly and disruptive.
There are known software techniques for ameliorating this problem, by digitising existing scanned images of buildings, etc., and pasting these onto three dimensional (3D) computer models, so creating a realistic 3D model. However, building such a 3D computer model is cumbersome.
From patent publication WO/01/1685 there is known a method for real-time segmentation of video objects in known stationary image background. This method uses segmentation of foreground objects calculated by average value of several takes of individual image pixels. Foreground objects are marked, and the method ensures that background is not considered as foreground because of change in light conditions.
From U.S. Pat. No. 6,078,619 there is known an object-oriented video system implemented as a two-layer object model in a video compressor system. In this system bandwidth is reduced by not sending full pictures, there being less information in the background layer.
From U.S. Pat. No. 6,301,382 there is known a method for extracting a matte of a foreground object from a composite image by filming against two completely different backgrounds.
From U.S. Pat. No. 5,915,044 there is known a scheme for encoding video images using foreground/background segmentation. This scheme sends less data for background segments so as to concentrate bandwidth on foreground segments.
From U.S. Pat. No. 5,914,748 there is known a scheme for generating a composite image using the difference of two images. This scheme requires a clean background in order to obtain a fragment object, which is then placed as a foreground object on a new background.
From a demonstration published at the website http://www.cs.huji.ac.il/labs/vision/demos/removal/removal.html it is known to remove a moving object from a video stream of image frames by (i) using optical-flow to identify and track the moving object and to blacken its pixels and (ii) using pixels from subsequent frames to substitute for the blackened pixels. However, this demonstrated technique uses only a single copy of each image, resulting in a low quality end result.
A need therefore exists for method and arrangement for removal of moving objects from a video stream wherein the abovementioned disadvantage(s) may be alleviated.